Answer: Hydropower & Fossil Fuels
Hydropower is renewable energy derived from the gravitational force of falling or flowing water. It converts the potential and kinetic energy of water into electricity through turbines and generators, making it one of the oldest and most reliable sources of clean electricity.
Working Principle
Water stored at elevation (dam reservoir) possesses potential energy. When released through penstocks, it gains kinetic energy. This high-velocity water strikes turbine blades, converting kinetic energy to mechanical energy (rotation). The turbine shaft drives a generator, converting mechanical energy to electrical energy.
Power Formula: P = ρ × g × h × Q × η
Where: P = Power (kW), ρ = water density (1000 kg/m³), g = gravity (9.8 m/s²), h = head (m), Q = flow rate (m³/s), η = efficiency
Types of Hydropower Plants
| Type |
Description |
Capacity |
| Large Hydro |
Major dams with large reservoirs |
>25 MW |
| Small Hydro |
Run-of-river, minimal storage |
2-25 MW |
| Mini Hydro |
Local grid supply |
100 kW - 2 MW |
| Micro Hydro |
Village/household scale |
<100 kW |
| Pumped Storage |
Energy storage - pumps water up during low demand |
Variable |
Advantages
- Clean Energy: No direct CO2 emissions during operation
- Renewable: Water cycle continuously replenishes
- Reliable: Can operate 24/7 with consistent output
- Long Lifespan: Plants operate 50-100+ years
- Grid Balancing: Quick start/stop for peak demand
- Multipurpose: Irrigation, flood control, water supply
- Energy Storage: Pumped storage acts as giant battery
Disadvantages
- High capital cost and long construction time
- Environmental impact: habitat disruption, fish migration barriers
- Social impact: displacement of communities
- Sedimentation reduces reservoir capacity
- Dependent on rainfall and water availability
Hydropower in India
- Installed: ~47 GW (including pumped storage)
- Potential: 145 GW exploitable
- Major Projects: Tehri (2400 MW), Bhakra-Nangal, Koyna, Sardar Sarovar
- Key States: Himachal Pradesh, Uttarakhand, Karnataka, J&K
Fossil Fuels are hydrocarbon-based energy sources formed from decomposed remains of ancient organisms over millions of years (300-400 million years). They include coal, petroleum (crude oil), and natural gas, which store ancient solar energy in chemical bonds.
Types of Fossil Fuels
| Type |
Formation |
Composition |
State |
| Coal |
Plant matter in swamps under pressure |
Carbon-rich |
Solid |
| Petroleum |
Marine organisms under heat/pressure |
Hydrocarbons |
Liquid |
| Natural Gas |
Similar to oil, less pressure |
Methane (CH4) |
Gas |
Applications
- Power Generation: Coal thermal plants (70% of India's electricity), gas turbines
- Transportation: Petrol, diesel, aviation fuel, CNG, LNG
- Industry: Steel (coking coal), cement, chemicals
- Domestic: LPG cooking, kerosene
- Petrochemicals: Plastics, fertilizers, pharmaceuticals
Advantages
- High Energy Density: More energy per unit mass/volume
- Established Infrastructure: Extraction, transport, distribution networks
- Reliable: Dispatchable, available on demand
- Affordable: Currently cheaper in many applications
- Versatile: Multiple end uses from single source
Disadvantages
- Non-Renewable: Finite reserves, will deplete
- Climate Change: CO2 emissions causing global warming
- Air Pollution: SOx, NOx, particulates, smog
- Environmental Damage: Mining, oil spills, habitat destruction
- Health Impacts: Respiratory diseases, cancer
- Price Volatility: Geopolitical factors affect supply/price
- Energy Security: Import dependence for many countries
Global Energy Share: Fossil fuels: ~80% | Coal: 27% | Oil: 31% | Gas: 24% | India imports ~85% oil and ~50% gas
Transition Away from Fossil Fuels
- Paris Agreement commitment to limit warming
- Renewable energy becoming cost-competitive
- Electric vehicles replacing ICE vehicles
- Coal power plant retirements accelerating
- India's Net-Zero 2070 target driving change
Sources: Module 2 Notes | IEA | MNRE | CEA